In 1932, excavators in the Athenian Agora discovered a disturbing deposit one of the wells on the site. The skeletons of hundreds of infants and dogs were recovered from debris deposited after the well ceased to be used as a water supply. The mass of infant burials led to much speculation, and possible explanations for the large number of infant skeletons included a cult of infant sacrifice, previously undocumented plague, and association with military disaster. A recent multi-disciplinary project has at last clarified the date and nature of the deposit, and provides insight into the high infant mortality rates that plagued the ancient city. This lecture examines the causes of death of nearly 450 infants deposited in the well, and explores the possible explanations for the creation of this unusual mass grave.